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Title: Laser surface modification of carburized and borocarburized 15CrNi6 steel

Abstract

The paper presents the results of laser heat treatment (LHT) of carburized and borocarburized 15CrNi6 low-carbon steel. Laser tracks were arranged by CO{sub 2} laser beam as multiple tracks formed in the shape of a helical line. The microstructure and properties of these diffusion layers were compared with those obtained after through-hardening. The microstructure after carburizing and LHT consists of adjacent characteristic zones: re-melted zone (coarse-grained martensite), carburized layer with heat affected zone (fine acicular martensite), carburized layer without heat treatment and the substrate (ferrite and pearlite). The highest measured microhardness (about 820 HV) was observed in re-melted and heat affected zones. The increase of distance from the surface was accompanied by a gradual decrease of microhardness up to 400 HV beneath the HAZ and up to 250 HV in the core of steel. The carburized layer after LHT exhibited a higher resistance to frictional wear compared to a carburized layer after through-hardening. The microstructure after borocarburizing and LHT consists of the following characteristic zones: iron borides of laser-modified morphology (FeB and Fe{sub 2}B), carburized layer with heat affected zone (martensite and alloyed cementite), carburized layer without heat treatment and the substrate (ferrite and pearlite). The highest microhardness was obtainedmore » in the iron boride zone. The microhardness of FeB boride extended up to 2200 HV and for the Fe{sub 2}B boride up to about 1300-1600 HV. With increased distance from the surface, the microhardness gradually decreases to 800 HV in HAZ, 400-450 HV in the carburized layer without heat treatment and to 250 HV in low-carbon substrate. The iron borides after LHT assume a globular shape, which leads to a lower texture and porosity of the borided layers. The increased resistance to friction wear of the borocarburized layers is certified in comparison with the borided layer after conventional heat treatment (through-hardening)« less

Authors:
 [1];  [2]
  1. Poznan University of Technology, Institute of Materials Science and Engineering, Pl. M.Sklodowskiej-Curie 5, 60-965 Poznan (Poland). E-mail: coolka@sol.put.poznan.pl
  2. Poznan University of Technology, Institute of Materials Science and Engineering, Pl. M.Sklodowskiej-Curie 5, 60-965 Poznan (Poland)
Publication Date:
OSTI Identifier:
21003555
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Characterization; Journal Volume: 58; Journal Issue: 5; Other Information: DOI: 10.1016/j.matchar.2006.06.010; PII: S1044-5803(06)00204-X; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CARBON DIOXIDE LASERS; CARBON STEELS; CEMENTITE; FERRITE; FERRITES; HARDENING; HEAT AFFECTED ZONE; HEAT TREATMENTS; IRON BORIDES; MARTENSITE; MICROHARDNESS; MICROSTRUCTURE; MORPHOLOGY; PARTICLE TRACKS; POROSITY; SUBSTRATES; WEAR RESISTANCE

Citation Formats

Kulka, M., and Pertek, A. Laser surface modification of carburized and borocarburized 15CrNi6 steel. United States: N. p., 2007. Web. doi:10.1016/j.matchar.2006.06.010.
Kulka, M., & Pertek, A. Laser surface modification of carburized and borocarburized 15CrNi6 steel. United States. doi:10.1016/j.matchar.2006.06.010.
Kulka, M., and Pertek, A. Tue . "Laser surface modification of carburized and borocarburized 15CrNi6 steel". United States. doi:10.1016/j.matchar.2006.06.010.
@article{osti_21003555,
title = {Laser surface modification of carburized and borocarburized 15CrNi6 steel},
author = {Kulka, M. and Pertek, A.},
abstractNote = {The paper presents the results of laser heat treatment (LHT) of carburized and borocarburized 15CrNi6 low-carbon steel. Laser tracks were arranged by CO{sub 2} laser beam as multiple tracks formed in the shape of a helical line. The microstructure and properties of these diffusion layers were compared with those obtained after through-hardening. The microstructure after carburizing and LHT consists of adjacent characteristic zones: re-melted zone (coarse-grained martensite), carburized layer with heat affected zone (fine acicular martensite), carburized layer without heat treatment and the substrate (ferrite and pearlite). The highest measured microhardness (about 820 HV) was observed in re-melted and heat affected zones. The increase of distance from the surface was accompanied by a gradual decrease of microhardness up to 400 HV beneath the HAZ and up to 250 HV in the core of steel. The carburized layer after LHT exhibited a higher resistance to frictional wear compared to a carburized layer after through-hardening. The microstructure after borocarburizing and LHT consists of the following characteristic zones: iron borides of laser-modified morphology (FeB and Fe{sub 2}B), carburized layer with heat affected zone (martensite and alloyed cementite), carburized layer without heat treatment and the substrate (ferrite and pearlite). The highest microhardness was obtained in the iron boride zone. The microhardness of FeB boride extended up to 2200 HV and for the Fe{sub 2}B boride up to about 1300-1600 HV. With increased distance from the surface, the microhardness gradually decreases to 800 HV in HAZ, 400-450 HV in the carburized layer without heat treatment and to 250 HV in low-carbon substrate. The iron borides after LHT assume a globular shape, which leads to a lower texture and porosity of the borided layers. The increased resistance to friction wear of the borocarburized layers is certified in comparison with the borided layer after conventional heat treatment (through-hardening)},
doi = {10.1016/j.matchar.2006.06.010},
journal = {Materials Characterization},
number = 5,
volume = 58,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}
  • This paper presents a design of experiment (DOE) for laser surface modification process of AISI H13 tool steel in achieving the maximum hardness and minimum surface roughness at a range of modified layer depth. A Rofin DC-015 diffusion-cooled CO{sub 2} slab laser was used to process AISI H13 tool steel samples. Samples of 10 mm diameter were sectioned to 100 mm length in order to process a predefined circumferential area. The parameters selected for examination were laser peak power, overlap percentage and pulse repetition frequency (PRF). The response surface method with Box-Behnken design approach in Design Expert 7 software wasmore » used to design the H13 laser surface modification process. Metallographic study and image analysis were done to measure the modified layer depth. The modified surface roughness was measured using two-dimensional surface profilometer. The correlation of the three laser processing parameters and the modified surface properties was specified by plotting three-dimensional graph. The hardness properties were tested at 981 mN force. From metallographic study, the laser modified surface depth was between 37 {mu}m and 150 {mu}m. The average surface roughness recorded from the 2D profilometry was at a minimum value of 1.8 {mu}m. The maximum hardness achieved was between 728 and 905 HV{sub 0.1}. These findings are significant to modern development of hard coatings for wear resistant applications.« less
  • The change in magnetic properties, hardness, and microstructure of the carburized case of the teeth of 20Kn2N4A steel gears with various heat-treatment cycles was investigated. It was established that the field of residual magnetization may be used as a parameter for nondestructive determination of the hardness and microstructure of the carburized case of 20Kh2N4A steel parts. Production inspection has been introduced with the use of the ION-2M instrument.
  • High cycle fatigue properties of gas-carburized 4140 steel were assessed to compare with those of 8620 steel which is widely used as a carburizing steel. Fatigue limit was evaluated associated with microstructure, case depth, and distribution of retained austenite and compressive residual stress near the surface. Test results indicated that the reheat quenching method of 4140 and 8620 steels produced a reduction in grain size, retained austenite level, and compressive residual stress at the surface and an increase in fatigue limit. The fatigue limit of direct-quenched 4140 steel shows substantially lower value than that of direct-quenched 8620 steel due tomore » larger grain size of direct-quenched 4140 steel. However, the fatigue limit of reheat-quenches 4140 steel is greatly improved and is comparable to the reheat-quenched 8620 steel. This is attributed to the larger reduction ratio in grain size and deeper case depth of reheat-quenched 4140 steel as compared to direct-quenched and reheat-quenched 8620 steels.« less
  • In failure analysis, in order to determine whether a component has failed under monotonic or cyclic loading, it is sometimes necessary to develop standards for each type of failure, especially when the fracture surface of a part that has failed in service contains features which may be ambiguous in their interpretation., Such is the case in the present instance, where in order to categorize the fractographic features of an AISI 9310 carburized steel, failures under monotonic and cyclic loading had to be obtained. The specimens were round bars which contained a circumferential semicircular notch, and were loaded in four-point bending.more » The effective case depth of the carburized layer was 1 mm, with a hardness of 60 HRC. The core hardness was 40 HRC (R{sub C}). Under monotonic loading, a circumferential crack developed in the case near the case-core interface, and striationlike markings were observed at low magnification on the fracture surface of the core which might be interpreted as fatigue markings. On the other hand, under cyclic loading, no circumferential cracks were observed in the case near the fracture origin, but they did develop in the region of final separation. In addition, the fracture surface in the core was markedly different in appearance from that obtained under monotonic conditions. These differences were further established by scanning electron microscopy analysis. The factors giving rise to the various fractographic features are discussed.« less